


Hypothetically

by StarlightDragon



Category: Supernatural
Genre: Alternate Universe - High School, Alternate Universe - Human, Bottom Dean, First Time, Friends to Lovers, M/M, Top Castiel
Language: English
Status: Completed
Published: 2015-06-02
Updated: 2015-06-02
Packaged: 2018-04-02 13:36:32
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,507
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/4061950
Author URL: https://archiveofourown.org/users/StarlightDragon/pseuds/StarlightDragon
Summary: <blockquote class="userstuff">
              <p>Dean wonders aloud who would be the top if he and his best friend Castiel were in a relationship. It's a completely hypothetical question, until it's not.</p>
            </blockquote>





	Hypothetically

**Author's Note:**

> I tried to write smut but I kept wanting them to just be really cute, so I'm sorry.
> 
> Again (I seem to be making a habit out of this) this is based on a tumblr post, which can be found here. http://aph-badtouchtrio.tumblr.com/post/120194686076/aph-badtouchtrio-aph-badtouchtrio The fact that I think 'Destiel AU' for every single tumblr post I see is going to get me into trouble one of these days.

“So, dude, hypothetically, if we were gay, like a gay couple, which one of us would be the top?”

Sam almost choked as he walked past his brother’s door on his way to grab some food from the kitchen. There was no _way_ he’d just heard that. There was no possible way his brother had just made those words, with his _mouth_. Sam was going to be scarred for life here.

But if he _had_ just heard what he thought he’d heard, well, there was only one person who could plausibly be in there with him.

Impossibly curious, although at the same time hating himself for it, Sam sat down on the floor and propped his ear against the door.

Inside the room, Dean was lying sprawled across his bed playing on his phone, while his best friend Castiel was sitting cross legged on the floor, a textbook open on his lap. Dean had finished some of his homework and didn’t want to do the rest of it, so he was trying to distract Cas from studying. Bribery hadn’t worked, repeatedly saying his name in ever more annoying voices hadn’t worked, so now he was going with the shock tactics.

“I would,” Cas replied, sounding unconcerned, and infuriatingly, he made it seem like there was absolutely no room for discussion. He didn’t look up. He just kept reading.

Dean was about to get annoyed when he realized something. The way Cas had said it, with that kind of confidence… did that mean he’d thought about this before?

Dean shifted a little in his position on the bed.

“No, I think my dick is bigger, so I’d top,” Dean said after a moment, all false confidence and manly bravado.

For the first time, Castiel turned to look at Dean, and he seemed like he was genuinely contemplating this. After a long pause, he determined, “No, I think mine’s bigger,” and turned back to the chemistry book.

Dean turned to glare at Cas, infuriated. How could he sit there looking so calm about this whole thing? This was a very serious issue, and not something the two of them could take lightly. And there Cas was, completely making assumptions about Dean. Assumptions he had no idea about.

“Oh yeah? Wanna check?” Dean challenged in his anger.

Castiel folded down the corner of his page and closed the book. “If it would make you feel better.”

Cas stood up and reached for the zipper on his jeans, looking completely unaffected, like getting naked in front of Dean was no big deal.

Not one to back down from a challenge, especially not one he’d started, Dean stood up too and tugged off his sweatpants, followed by his boxers. They got caught around his ankles and for a moment he did an ungainly dance around the room as he tried to shake them off, and when he managed to right himself once more, he was greeted by the sight of a half naked Castiel.

And, _wow._

Cas was _huge._ Dean would never admit to paying attention to the cocks he saw in porn, but _if_ he did, then he was sure that Cas was at the very least comparable with most of them. Dean had never had cause to complain when it came to himself, and certainly none of the girls he’d slept with had ever had any problems with his size, but at the same time, he knew he was nothing special. Cas, on the other hand… All he was saying was that a cock like that certainly deserved more use than Cas’s currently got.

“Bro, you’re fucking _hung_ ,” Dean breathed, almost reverently.

Cas’ head snapped up, and it could have been Dean’s imagination, but maybe Cas’ eyes were a little darker than usual. “Yes, I’m statistically large. I see my prediction was right.” He gestured towards Dean’s own cock.

Dean blushed and twisted away, trying to hide himself, and Cas seemed to understand that he’d made a mistake. “Not that I see any problems with your own size. You are very… aesthetically pleasing.”

Aesthetically pleasing. Dean supposed he would accept that.

“Do you mean I’m hot, Cas?” Dean teased, looking up through his lashes, because the two of them were almost naked now, and things were going to be awkward between them later anyway, so Dean might as well push as far as he could.

Cas sighed, a long, shuddering breath, and he was definitely affected by this in some way. “Yes, Dean. I’m saying you’re hot,” he finally admitted.

Dean stepped a little closer to Cas, not entirely consciously aware he was doing it. He’d be lying if he said he’d never thought about the possibility of something happening between him and Cas before. There was a reason the idea had floated so quickly to the top of his mind when he’d been trying to get a rise out of Cas. And he was certainly getting that now, he saw, as his gaze returned to Castiel’s cock.

Dean had never, ever intended to act on those thoughts, though. That was reserved for his dream self, the one who he could insist was outside of his control, even when he woke up shaking in pleasure wearing sticky underwear.

Then again, it was easy to say you’d never sleep with your best friend when he was over the other side of the room, fully clothed, trying to convince you to go back to your schoolwork. It was a little more difficult when he was standing right in front of you, naked and hard, eyes boring into yours like he was waiting for something.

Before Dean could stop himself, he took another step forwards so that he was close enough to feel Castiel’s breath on his face, and he crashed his lips into Cas’, his hand reaching up to grasp Cas’ hair when it seemed like the other boy might be about to stumble backwards. Cas’ mouth opened – in shock, or in pleasure, or in both, Dean couldn’t tell, but some part of his brain registered that Cas was kissing back so he must be okay with this, so Dean kept going, flicking his tongue into Cas’ mouth just so that he could taste more of him, the pressure of Cas’ lips on his sending sparks through his body, his own cock reaching full hardness and throbbing with its need to touch Castiel’s.

Finally, Dean pulled back, gasping for air.

“What was that?” Castiel asked, breathless himself.

“I kissed you. I thought you might have figured that out.”

“I thought this was a hypothetical question?” Cas suddenly looked concerned.

“Yes, but we never reached a _decision_.”

There was a pause, and then Cas lunged towards Dean, kissing him again even harder than before.

“I think you’ll find we did,” he growled into Dean’s mouth, and then he was gripping Dean by the shoulders and pulling the two of them tight together, Dean’s cock rubbing up against Cas’, and Dean moaned in surprise.

Outside, Sam heard Dean's moan, and it finally clicked for him what was going on. Dean and Cas were... No. No, no, no. Sam was out of here. He did not want to think about his brother doing that with anyone, let alone awkward, nerdy Cas who had sat next to Sam at uncountable family dinners over the past few years. And, sure, he'd teased Dean about maybe having feelings for Cas before, but he'd never, ever expected to be right.

He stood up and jogged down the stairs, on his way to get that food and then take it into the yard, or maybe to another street.

“Cas… someone might hear us,” Dean protested, not really putting any conviction into it.

“Suppose I’ll have to make sure you shut up, then.”

Dean didn’t know what Cas meant until there was a hand over his mouth and lips kissing all over his neck and collarbone, occasionally startling him by biting down lightly, and when Dean moaned again, louder than before, it was muffled by Cas' hand. Dean’s legs were trembling underneath him so he wrapped his hands around Cas’ waist to hold himself steady, and then before he knew what was happening, Cas was pulling him down and he was toppling over onto the bed with a bounce.

He barely had time to process this before Cas was back, crawling on top of Dean and lifting him up to pull his shirt off. Dean had had no idea Cas was so _strong._ He was learning all kinds of new things today.

“Yours too,” Dean panted once the shirt was in a far corner of the room, needing to feel Cas pressed against him with nothing separating them, and Cas didn’t need telling twice, hurriedly undoing his buttons and tossing his own shirt aside.

Cas sat astride Dean and just held eye contact with him for a minute, before he leaned down and very deliberately started kissing and licking a line down Dean’s chest; soft, teasing touches that had Dean shaking before Cas even reached his stomach, and Dean had to turn and bury his head in a pillow for fear of crying out.

When Cas reached Dean’s hips, he looked up at Dean one more time, then, seeing that Dean’s eyes had found his again, carefully slid his lips over the head of Dean’s cock.

Dean bit down hard on the pillow, fisting his hands into the sheets because he needed to do something with his body to respond to the sensation that was shooting through him right now. Cas’ mouth was on his cock. Cas’ mouth was sucking him down, tongue flicking over his slit to contrast the intense suction that had to be at least halfway down his cock right now, and Dean felt every nerve in his body responding. He was sure that in his dreams Cas hadn’t been half as smooth or practiced as this. Maybe he really wasn’t. Maybe it was just the fact that it was Cas that was making Dean struggle to keep his hips still on the bed, that was making his eyes water with the effort of keeping still and quiet.

He felt his cock twitch in Cas’ mouth, felt the pressure intensifying and his stomach tensing up as he prepared for-

Cas pulled off, sitting himself on top of Dean’s legs and wiping a strand of Dean’s precome from his mouth.

“You know I can’t fuck you if you come in my mouth, right?”

Dean’s cock throbbed at those words, aching to get Cas’ mouth back, and as much as he did want Cas to fuck him, he wasn’t sure if he could wait that long. He was so tempted to put his hand on his cock right now. He knew it would only take a few strokes before he’d be coming all over Cas’ face.

“You have lube, right?” Cas asked, and the temptation was gone, because suddenly this was a reality and there was no way Dean was going to pass up the chance of Cas fucking him, especially considering it could very well be his only chance.

He pointed towards the bedside table. “Top drawer.”

Cas climbed off of him, and Dean was suddenly cold, twisting around just to make sure Cas was still there. He was grateful that it didn’t take Cas long to find the lube, return to the bed and kiss him again. Dean had only kissed Cas for the first time maybe fifteen minutes ago, but already he missed his lips so much. He wasn’t sure how he’d ever been without them.

“Cas, please,” he whispered as Cas ran his hands down Dean’s chest, “I need you.”

Cas pulled away, his eyes wild and out of control for a second, before he collected himself enough to open the lube and squeeze some onto his palm.

“You’ve done this before, right?” he asked as he trailed one finger over Dean’s cock, then his balls, and down to his hole.

“With my fingers,” Dean whined, pushing into Cas’ touch, “never with anything as big as you.”

Cas nodded. “I’ll go slow. Tell me if you want me to stop.”

“I will,” Dean promised, and with that assurance, Cas pushed one finger inside Dean.

Dean gasped, grabbing the pillow to press over his face once more. Part of Castiel was inside him, his brain reminded him over and over again until the words no longer made sense, because things this good happened to him _never_ , and there was no way that was _Castiel’s_ finger lightly stroking his prostate, and surely he was going to wake up in a moment, except for the part where he didn’t. He was still there and Cas was still real and this had to be the most amazing thing Dean had ever felt.

When Cas pushed a second finger in, stretching Dean out, Dean revised that statement, because for sure this was even better.

“You okay?” Cas asked, stilling his fingers from where they’d been scissoring Dean, and Dean realized that his eyes were screwed shut and his face was contorted.

“Yeah,” Dean choked out. “It doesn’t hurt. It just feels so _much._ But please, don’t ever stop.”

Cas started thrusting again, far too slowly, and Dean bucked forwards onto Cas’ fingers, trying to fuck himself on them, just attempting to get Cas to speed up. Cas put a hand on Dean’s hip, pinning him down against the bed, again with that strength that Dean had had no idea he possessed. Cas continued to move his fingers in and out of Dean, occasionally twisting them against Dean’s prostate and pulling a stuttered gasp out of Dean.

Cas pushed a third finger inside, and it didn’t hurt exactly, but Dean was hyperaware of how full he suddenly was, And even though this was already better than anything Dean had anticipated might happen today, he was greedy, and he still wanted more. He hadn’t even had a chance to touch Cas’ cock properly yet, and he ached all over with how much he wanted it inside of him. Just the thought of Cas's cock filling him up was enough to have him biting his own lip in an attempt to stop himself from coming too soon.

“Cas,” he whined, reaching to grab the arm of Cas’ that was currently pinning him down, “please, I’m ready, fuck me now.”

Cas stopped moving his fingers, but kept them inside Dean. “Really? Because earlier you said you’d be the top in this relationship, and I’m getting some very mixed messaged here.”

Dean groaned. “I’m sorry, Cas, I didn’t know what I was talking about… you were right… _please_ …”

Cas held eye contact with Dean for another moment, not doing anything, and Dean held his breath, absolutely terrified that Cas was going to pull his fingers out, get up and put his clothes back on; that he’d only been trying to prove a point to Dean.

But no, Dean knew that Cas would never do anything like that. Cas smiled at Dean, a beautiful smile unlike any that Dean had seen from him before, and said, “Of course I will.”

He slid his fingers out of Dean and reached for the lube and a condom, leaving Dean suddenly feeling empty and far too far away from Cas. His cock jerked as he watched Cas cover his own in lube, both of them leaking precome, but even though Dean was desperate to come, he’d lost the immediate desire to touch himself. All he wanted was Cas, all over him, touching him in every way possible.

Cas lined himself up with Dean’s entrance, and Dean closed his eyes. He expected to feel Cas pushing in, but instead he felt Cas’s lips dropping a soft kiss onto his own, reassuring him that he was going to be alright.

Dean felt himself relax, sinking into the mattress. He hadn’t realized how tense he’d been. 

And _then_ he felt Cas pressing into him, and it seemed to Dean that there was no way this could work. Cas was much bigger than three fingers; definitely bigger than anything Dean had had inside him before, and he was pushing against Dean’s hole but he wasn’t going to fit, it just wasn’t _possible_ , Dean realized in frustration.

And then-

Dean squeaked out loud when the head of Cas’ cock pushed past that tight ring of muscle.

“Holy shit, Cas,” he whispered.

Cas’ fingers had been amazing, but they were nothing compared to feeling the hot, heavy weight of that amazing cock inside of him, filling Dean up, somehow managing to push in further and further every time Dean thought he couldn’t possibly take any more. It hurt, but it wasn’t like any other kind of pain Dean had experienced. It was more like an intense, unrelenting pressure, of him clamped so tightly around Cas that he could feel every single twitch of Cas’ cock.

Finally, Dean felt Cas’ balls press against his ass, and he heard Cas panting above him. He looked up to see Cas covered in sweat, gritting his teeth together and grimacing.

“I’m okay, Cas. You can move,” Dean reassured him.

Cas shook his head. “Not yet. If I move now, I’ll-“

Dean nodded in understanding, remembering how sensitive he’d been his first time fucking someone. But he needed something to distract himself, something to stop himself from lifting himself up and fucking himself on Cas’ cock, like every instinct was telling him to do right now.

Somehow, Cas seemed to understand this, and he grasped Dean’s cock in his hand, pumping it slowly. Dean whimpered, biting his own lip, every sensation intensified now that Cas was inside of him, and maybe this hadn’t actually been a great idea because now he wanted to move even more, to get more and more friction from Cas’ hand.

It was okay, though, because as he thought this, Cas began to slowly thrust into Dean, very slowly, looking like it was taking every bit of his concentration to manage this. Dean’s lips parted in a silent cry as Cas thrust in for the second time, right onto Deans prostate, at exactly the same time his hand twisted around the head of Dean’s cock, and Dean felt like he was going to explode.

No longer able to control himself, he grabbed at Castiel, scratching up and down his back, and Cas responded by moaning Dean’s name and speeding up his thrusts, Dean lifting himself off the bed to meet them, the mattress squeaking but both of them past the point where they could do anything about it; both of them sure they couldn’t stop now even if they wanted to.

Cas was hitting Dean’s prostate on every thrust; his hand had the perfect grip on Dean’s cock; his other hand had somehow threaded into Dean’s hair, tugging on it; and his weight was pressing down on top of Dean, and it was all too much for Dean to take. He felt his orgasm rise up inside him and he stilled his hands on Cas’ back, just holding on tight to his waist now, crying out.

“Cas, Cas, Cas, Cas… CAS!” His orgasm hit and his whole body tightened up, freezing as white strands of come burst from his cock, coating Cas’ hands and stomach, a thousand colors swirling behind his eyes.

Cas groaned, stroking Dean through his orgasm even as his own hips started to falter, stuttering now that Dean was suddenly clenching even tighter around him, and with a final thrust he exploded inside of Dean before collapsing on top of him, exhausted.

It was a few minutes before Dean could recover any thoughts that weren’t ‘Cas, that was amazing, you’re amazing, I’ve never felt that good in my life,’ but as the time passed and their breathing slowed to a normal rate, a few other concerns made their way into his head.

Firstly, there was no fucking way his entire family hadn't figured out exactly what had just happened here.

Secondly, Castiel was his best friend, and he’d potentially managed to fuck that all up by sleeping with him without thinking it through.

And thirdly, something he should have admitted to himself a long time ago: He definitely had feelings for Cas that went a long way beyond wanting to settle a bet.

With that in mind, and knowing it was now or never before the two of them left the room and all kinds of drama started, Dean shook Cas’ shoulder, waking him up from a half doze.

Cas opened his eyes, squinting at Deam. “Hmm?”

“So, Cas, hypothetically, if we were a couple, like a gay couple…” Dean said, terrified, searching Cas’ eyes for any emotion he might be able to read, to tell him whether he should finish his question. None came, but he carried on anyway. “Where would you take me on our first official date?”

“Hypothetically?” Cas confirmed.

Dean nodded. “Hypothetically. Although, less hypothetically, I don’t have plans tonight.”


End file.
